System for automatically controlling the tuning of television receiver receiving channels

ABSTRACT

A video receiving device (A) that includes a circuit for receiving first video signals from a remote transmitter, a circuit for receiving second video signals from another video receiver (TVS), a circuit (TU1) for automatic searching for transmission channels, and a circuit (PC) for phase comparison between the vertical synchronization signals of the first video signals and the vertical synchronization signals of the second video signals that can output an &#34;outphasing&#34; signal that is used for controlling the operation of the automatic channel search circuit, wherein the video receiving device (A) also includes a control circuit (CC) that enables the video signals that it is receiving to be displayed for a pre-determined time on the other video receiver (TVS). The invention is applicable notably to the programming of video recorders, and to the automatic tuning of such a recorder to the channel being viewed on a TV receiver in order to enable simple and immediate recording of this channel.

BACKGROUND OF THE INVENTION

The invention relates to a device for video reception, in particular acontrol system for subjecting the channel selection of a video receiverto the channels of another video receiver. The invention is applicablenotably to the automatic tuning of a video cassette recorder (VCR)connected to a television (TV) receiver.

DESCRIPTION OF THE PRIOR ART

In known VCR machines, when a user wishes to record a TV program he mustadapt his VCR to the channel corresponding to the TV's receptionchannel. In practice, when selecting the channel on the VCR, he mustmake sure that the number of the selected channel appears on the VCR'sdisplay; this is the only way of making sure that the right channel hasbeen selected.

If we assume that such a user always has a TV receiver that can operateat the same time as the VCR he intends to use, the invention proposes touse the TV receiver for selecting the program (channel) to be recordedand for automatically adjusting the VCR to the channel selected on theTV receiver.

In these conditions, when the user wishes to record a TV programreceived via an antenna or a cable network, for example, he selects onhis TV receiver the channel on which the program will be broadcast. TheVCR connected to this TV will then be adjusted automatically to the samereceiving channel as the TV receiver. The European patent application EP0618 721 A2 describes a VCR fitted with a reception circuit that can betuned to several channels and connected to a TV receiver which in turncan be tuned to several receiving channels. Once the TV receiver istuned to a given channel, it displays the video signals and emits theaudio signals received while also feeding them to the VCR. The latteralso includes a circuit for comparing at least one component of thesignal received directly by the VCR with the corresponding component ofthe signal that the VCR receives from the TV receiver. This comparisoncircuit is designed to output an "equality" signal if the signalscompared are the same, i.e. when the two devices are tuned to the samechannel, and an "inequality" signal when this is not the case, in whichcase the VCR will automatically search for the channel being received bythe TV receiver. However, two different channels may have two verticalsynchronization signals in phase. In this case, the comparison circuitchances to validate the tuning of the VCR receiver on a channeldifferent from the one to which the TV receiver is tuned.

The object of the invention is liberate from this problem of tuning ofthe VCR receiver on a channel different from the one to which the TVreceiver is tuned in case two different channels have two verticalsynchronization signals in phase, which is a significant improvementover the device described in the patent application EP 0618 721 A2.

SUMMARY OF THE INVENTION

The present invention concerns a video receiving device (A) thatincludes a circuit for receiving first video signals from a remotetransmitter, a circuit for receiving second video signals from anothervideo receiver (TVS), a circuit for automatic searching for transmissionchannels, and a circuit for phase comparison between the verticalsynchronization signals of said first video signals and the verticalsynchronization signals of said second video signals that can output an"outphasing" signal that is used for controlling the operation of saidautomatic channel search circuit, wherein said video receiving device(A) also includes a control circuit (CC) that enables the video signalsthat it is receiving to be displayed for a pre-determined time on saidother video receiver (TVS).

An important characteristic of the invention is that said controlcircuit (CC) includes a timer (TIME) controlled by the control unit ofsaid video receiving device when it is informed that the phases of saidvertical synchronization signals are the same. Said timer orders, for apre-determined time period, the transmission of the video signalsreceived by said video receiving device to said other video receiver(TVS), along with a signal (PIN8) indicating to this other videoreceiver (TVS) that it must display these video signals.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and other advantages andcharacteristics will become clear on reading the following descriptionof an embodiment, taken only as a non-limitative example, makingreference to the appended figures, of which:

FIG. 1 is a an example of a circuit that can be used to implement theinvention;

FIG. 2 is the circuit according to the invention;

FIGS. 3 and 4 are flow charts explaining the operation of the system.

In television transmission systems, we observe that all the transmissionchannels do not have the same time origin. Even when two channelstransmit the same image from the same transmitter, the images of the twochannels are not perfectly in phase. More precisely, we observe that thevertical synchronization signals of the two channels are out of phase.Therefore, to determine whether two receivers are both tuned to the samechannel we can check that vertical synchronization signals of the twosignals are in phase.

In FIG. 1, one of the devices has circuits providing for thisverification.

For example, the device TVS is a TV receiver; it is tuned to a givenchannel and receives a program via its tuner TU2.

The receiving device A is a VCR, for example. The user wishes to recorda program while he is viewing it on the receiver TVS.

The VCR has a TV reception circuit or tuner TU1 that incorporates anautomatic channel searching circuit. A control unit CPU controls thisautomatic searching function of the tuner TU1 and also provides for thegeneral management of the recorder.

The circuit TU1 receives video signals VD1, for example via an antenna,and feeds them to a circuit VSD1 which detects the verticalsynchronization signal.

In addition, the receiver TVS feeds the video signals it is receiving tothe VCR via a cable such as a peritel cable. These video signals arereceived by another vertical synchronization signal detection circuitVSD2. The detection circuits VSD1 and VSD2 feed the times of detectionof the vertical synchronization signals to a phase comparator circuitPC. If these synchronization signals detected by the circuits VSD1 andVSD2 are out of phase, this means that the tuners of the video recorderVCR and the TV receiver are not tuned to the same receiving channel. Thephase comparator PC feeds an "outphasing" signal to the control unit CPUwhich then triggers the automatic channel search function in the VCR(see FIG. 4).

If the synchronization signals are in phase, the circuit PC sends an"in-phase" signal to the control unit CPU which then knows that the VCRis tuned to the same channel as the TV receiver. Moreover, this systemoperates continuously to detect any change of channel. The control unitCPU is then ready to receive an instruction from the user, a recordinstruction for example.

The system according to the invention can also be used to program theVCR, in other words to program the table of correspondences betweenprogram selection buttons and reception channels.

In this case, the receiver TVS having been programmed, for each program(channel) displayed on the receiver TVS, the control unit CPU of the VCRis set to programming mode and given a first channel number. Thismicroprocessor CPU then orders an automatic channel search whichcontinues until the vertical synchronization signal of the video signalreceived from the antenna is in phase with the vertical synchronizationsignal of the video signal received from the TV receiver TVS. When thetwo signals are found to be in phase, this means the recorder is tunedto the same channel as the receiver TVS; the control unit CPU isinformed and this unit then memorizes the channel number and the programnumber in a program memory.

The user can then change the program (and therefore in principle thechannel) on his TV receiver TVS. He then sends another command to thecontrol unit CPU to put it in programming mode and chooses a secondprogram number. The search processes described previously is thenrepeated: the automatic channel search circuit searches for the samechannel as the one received by the TV receiver, then the control unitCPU memorizes the channel number identified in a program memory. Thisprocess can be repeated to memorize all the programs.

In order to be sure that the VCR is correctly tuned to the same channelas the one displayed on the TV receiver, either in programming mode orrecording mode of the VCR, a control circuit CC is provided as shown inFIG. 2. This includes a timer circuit TIMER that is activated either bya signal ENR (in recording mode), or by a signal PRG in programming modeand that transmits the video images received by the VCR to the receiverTVS via the peritel cable by closing the switch C1 for a predeterminedtime. At the same time, a slow switching signal is sent to the pin(PIN8) of the peritel connector to ensure that the TV receiver TVSconnects its reception circuits (via switches C1 and C2) to the peritelcable in order to display on the screen the video signals from the VCR.At the end of the predetermined time the voltage on PIN8 is dropped, therecorder applying a zero voltage so that the receiver reconnects itscircuits to the antenna. In this manner, for a short time determined bythe timer TIME the user can view the video program that the VCR isreceiving and recording.

FIG. 3 is a flow chart explaining the operation of a system that enablesthe program memory of one receiver, TVS for example, is copied into thatof another receiver such as the VCR.

In a first step, the user selects the first program on the receiver TVSand switches the receiver VCR to programming mode.

In the VCR the system searches for the reception of the same channel asthe receiver TVS by comparing the phases of the vertical synchronizationsignals received by the two devices. As long as these signals are out ofphase the system repeats the search on the next channel. Once asynchronization of the phases is detected, the channel number ismemorized with the program number. A signal is sent to the user toconfirm that the program has been memorized. The user can then stop theprogramming, or he can continue by selecting the next program on thereceiver TVS, in which case another automatic programming cycle isperformed, and so on.

In the description above, the invention is explained with reference to avideo recorder (VCR) and a television receiver. However, it is clearthat the principle is applicable to any other type of device capable ofreceiving video programs.

What is claimed is:
 1. A video receiving device including a circuit forreceiving first video signals, a circuit for receiving second videosignals from another video receiver, a circuit for automatic searchingfor transmission channels, and a circuit for comparing a phase betweenthe vertical synchronization signals of said first video signals and thevertical synchronization signals of said second video signals andproviding an "outphasing" signal used for controlling the operation ofsaid automatic channel search circuit based upon the comparison, whereinsaid video receiving device also includes a control circuit for enablingthe first video signals to be displayed for a predetermined time on saidanother video receiver.
 2. Video receiving device according to claim 1,wherein said video receiving device (A) is a video recorder (VCR) andincludes a control unit (CPU) that controls the operation of said videorecorder and said automatic channel search circuit (TU1), said controlunit activating said automatic channel search circuit for as long assaid phase comparison circuit detects that said vertical synchronizationsignals are out of phase, and deactivating said automatic channel searchcircuit when said phase comparison circuit detects that said verticalsynchronization signals are in phase.
 3. Video receiving deviceaccording to claim 2, wherein said control circuit includes a timer,wherein when said vertical synchronization signals are detected to be inphase, said timer directs the first video signals received by said videoreceiving device to said another video receiver for a predetermined timeperiod, along with a signal causing the another video receiver todisplay the first video signals.
 4. Video receiving device according toclaim 2, wherein said control unit (CPU) includes a program memory andmeans of operating in programming mode, said control unit (CPU)supplying a channel number detected when said phase comparison circuitdetects that said vertical synchronization signals are in phase, saidchannel number being memorized in said program memory along with apre-selected program number.
 5. Video receiving device according toclaim 2, wherein said control unit (CPU) includes means of operating inrecording mode, said operating means switching said video recorder intorecording mode when said phase comparison circuit detects that saidvertical synchronization signals are in phase.
 6. Video receiving deviceaccording to claim 1, including a peritel-type connector enabling saidvideo receiving device to be connected to said another video receiverand to receive said second video signals.